Renewing lease on late-paying tenant? Increase Security Deposit?

[Michael Zagorsky]

We have a townhouse that rents for $1,100/mo in Birmingham.  Professionally managed. We live out of state.  Signed new tenant in July of last year always paid on time.  Beginning in Jan of the tenant started to get 15 days late on the rent.  The lease has a $100 late fee split between the PM and us.  The lease is up in four months.  Here is my question:  Should I just refuse to resign the lease or just ask for a bigger security deposit with renewal (like $3,300?).  Reason I ask is that the PM will charge one month rent to find a new tenant plus vacancy and I figure asking for that big payment will cause the tenant to really ask herself if she can afford to stay there.